1. Field
The invention relates to controlled irrigation of agricultural fields, and, in particular, to a system for automatic furrow irrigation.
2. State of the Art
In furrow irrigation of agricultural fields, the furrows must transport water from the top or head ends thereof to the mutually respective bottom ends thereof and, in addition, provide the infiltration medium for the water to enter the soil. In accomplishing the infiltration function, water must be in contact along the full length of the furrow for a sufficient time to allow the required infiltration of water into the soil. If small streams of water are used, the required volume of water can be applied, but most of the water enters the soil near the head ends of the furrows, with little water infiltrating the soil at the bottom ends of the furrows. On the other hand, when a large stream is applied to the head ends of the furrows, the water advances rapidly to the bottom ends and must be allowed to runoff for a sufficient time to permit the required infiltration along the length of the furrow. The run-off is often wastefully lost.
Cutback methods have been proposed in which a large stream of water is applied to the head ends of the furrows during the initial stage of the irrigation wherein water is advanced rapidly to the bottom end of the furrows to reduce deep percolation at the head end of the furrows. When the water has advanced to the bottom ends of the furrows, the size of the stream of water introduced at the head ends is reduced to minimize the amount of run-off which occurs during the remaining infiltration stage of the irrigation. Heretobefore, the cutback in the flow of water to the head ends of the furrows has been achieved by providing a constant flow of water at a reduced rate of flow to the head ends of the furrows during the infiltration stage of the irrigation. Reducing the flow rate at the head ends of the furrows still tends to result in a shallower penetration of water at the bottom ends of the furrows than at the head ends.
3. Objectives
Principal objectives of the present invention are to provide a method and apparatus wherein effective cutback in the flow of water to the furrows during irrigation is achieved by providing intermittent flow of water to the head ends of the furrows instead of controlling the flow rate of a continuously flowing stream.